On-line version ISSN 1807-8621
Acta Sci., Agron. vol.34 no.2 Maringá Apr./June 2012
Mortalidade de Caryocar brasiliense no norte do Estado de Minas Gerais, Brasil
Germano Leão Demolin LeiteI, *; Aline Fonseca do NascimentoI; Sergio Monteze AlvesI; Paulo Sérgio Nascimento LopesI; Nilza de Lima Pereira SalesI; José Cola ZanuncioII
IInsetário George Washington Gomez de Moraes, Laboratório de Entomologia, Instituto de Ciências Agrárias, Universidade Federal de Minas Gerais, Av. Universitária, 1000, 39404-006, Cx Postal 135, Montes Claros, Minas Gerais, Brazil
IIDepartamento de Biologia Animal, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil
The purpose of this work was to study the percentage of healthy trees, living trees and healthy branches and the renewal (natural propagation) of Caryocar brasiliense associated with the properties of soil, the floristic diversity and the canopy size of this plant. Lower proportions of live C. brasiliense trees and of healthy branches were found in the Savanna of Ibiracatu, where only 30% of the trees were healthy and without visible signs of attack by wood borers and by Phomopsis sp. We observed that C. brasiliense trees in areas where the soils contained higher levels of summed chemical bases and total sand (fine + gross) were less healthy. Moreover, the areas whose soils contained higher levels of aluminum and clay had a higher percentage of healthy C. brasiliense trees and branches. Smaller percentages of live and healthy trees and healthy branches were noted in areas with higher floristic diversity. Overall, the higher mortality of C. brasiliense trees may be associated with a higher pH and a lower content of aluminum, silt and clay, with competition with other tree species for nutrients, water and light, with the attack of Cossidae and particularly with the attack of fungi, Phomopsis sp.
Keywords: pequi, canopy size, floristic diversity, Cossidae, Phomopsis sp.
O objetivo deste trabalho foi estudar a percentagem de árvores sadias, vivas, galhos sadios e taxa natural de regeneração (propagação natural) de Caryocar brasiliense, associando com propriedades do solo, diversidade florística e tamanho de copa desta planta. As menores percentagens de árvores vivas de C. brasiliense e de galhos sadios foram observadas no cerrado de Ibiracatu, onde somente 30% destas estavam saudáveis, sem sinais visíveis de ataque do broqueador de tronco (Lepidoptera: Cossidae) e do fungo Phomopsis sp. As árvores de C. brasiliense localizadas em áreas cujos solos continham maiores níveis de soma de bases e areia total (fina + grossa) estavam menos saudáveis. Além disso, as áreas cujos solos continham maiores níveis de alumínio e de argila apresentaram maiores percentagens de árvores de C. brasiliense sadias e de galhos sadios. As menores percentagens de árvores vivas e sadias e com galhos vigorosos foram notados em áreas com maior diversidade florística. A maior mortalidade de árvores de C. brasiliense pode estar associado com maior pH e menor conteúdo de alumínio, de silte e argila, aliado com a competição com outras espécies florestais por nutrientes, água e luz, associado com ataque de Cossidae e principalmente do fungo Phomopsis sp.
Palavras-chave: pequi, tamanho de copa, diversidade florística, Cossidae, Phomopsis sp.
The Savanna ecosystem occupies approximately 23% of the total area of Brazil and is high in plant diversity. The Savanna plant Caryocar brasiliense has a broad distribution in this ecosystem (ALMEIDA et al., 1998). Its fruits are used as food, in the production of cosmetics and lubricants and in the pharmaceutical industry (ARAÚJO, 1995). These fruits also represent the main source of income for many communities. However, uncontrolled harvesting has a strong effect on the propagation of C. brasiliense. Approximately 8.0 and 11.0% of plants up to 1.0 m in height (a relatively small percentage) and 60.0 and 45.0% taller than 3.0 m (reproductive phase) were observed in the Savanna and pasture areas, respectively (LEITE et al., 2006).
This information indicates that fruit collectors remove virtually all fruits from the tree. By doing so, they significantly reduce the propagation of C. brasiliense in the Savanna areas of Brazil (LEITE et al., 2006). Although the Savanna areas have been deforested, the C. brasiliense trees are left in the field. This situation increases their mortality (personal communication from collectors of C. brasiliense fruits) and the chance that they will be attacked by insects (LOPES et al., 2003; LEITE et al., 2007, 2009, 2011a, b, c and d).
Some studies have associated the mortality of C. brasiliense trees with the attacks of wood borers on the trunks (Lepidoptera: Cossidae) (LEITE et al., 2011b) and of the fungus Phomopsis sp. on the branches. However, we do not know the actual levels of mortality of C. brasiliense trees or the identity of other factors that may be involved in this mortality.
Several factors, such as the size of the tree canopy (FAN et al., 2008; ITO; KOBAYASHI, 1993; LEITE et al., 2011b; McCULLOUGH; SIEGERT, 2007; ZANUNCIO et al., 2002), the presence of environmental stresses (FREDERICKS; JENKINS, 1998; HANKS et al., 1999; LEITE et al., 2006, 2011b) and the floristic diversity (HEITZMAN, 2003; LEITE et al., 2011b) of the area, may directly or indirectly affect the plants and their herbivores and diseases.
The objective of this work was to study the percentage of healthy trees, live trees and healthy branches and the renewal (natural propagation) of C. brasiliense associated with the properties of soil, the floristic diversity and the canopy size of this plant in six Savanna and pasture areas of northern Minas Gerais State, Brazil.
Material and methods
This work was conducted in the Municipalities of Montes Claros and Ibiracatu, northern Minas Gerais State, Brazil, in October 2006. The study investigated one area of Savanna vegetation sensu stricto and three areas with pastures (prior Savanna) in Montes Claros and one Savanna vegetation sensu stricto and one pasture (prior Savanna) in Ibiracatu. Both municipalities have a tropical climate (Aw, Köppen classification) with a dry winter and a rainy summer. These areas exhibit different characteristics of soil and floristic diversity. The geographical coordinates, altitude, soil type, physiochemical characteristics of the soil, floristic density, crown height and crown width were recorded in each of the areas studied (Tables 1, 2, and 3).
The treatments used in the study consisted of the six areas (two savannas and four pastures). The experimental design was completely random and used 32 repetitions (32 trees per area). A total of 192 C. brasiliense trees were evaluated. In each area (~160 ha), we walked (~1600 m) in a straight line through the middle of the area.
Randomly every 50 meters, we selected a C. brasiliense tree and evaluated the following characteristics: tree health (without trunk borer attack, with live branches); whether the tree was alive; branch health (not dry or with early symptoms of fungal attack); the height and width of the canopy; and the trunk diameter at breast height (DBH) (by using a tape measure). We calculated the percentage of healthy trees and live trees in each area and the percentage of healthy branches per tree. Every 300 meters along the survey line, we evaluated the renewal (natural propagation) of C. brasiliense and the floristic diversity in an area of 1000 m2 by counting the number of trees groves-1 (> 2.0 m high) and shrubs (0.50 - 2.0 m high). The number of herbs (< 0.50 m high) and the percentage of cover were measured by placing a square at each of six points in each of the six 1000 m2 areas.
A total of 36 soil samples (0-20 cm deep) were collected, with six samples per area. The physical and chemical characteristics of the samples were evaluated at the Laboratory of Soil Analysis of the ICA/UFMG according to the methodology of Embrapa (1997). The samples were collected beneath the C. brasiliense canopies.
The data were examined with an analysis of variance and regression analysis (p < 0.05) was applied to relate the characteristics of the C. brasiliense trees to soil attributes and floristic diversity. The data were transformed using and examined with an analysis of variance and Scott-Knott test (p < 0.05).
Results and discussion
A relatively low proportion of living C. brasiliense trees were found in the Savanna of Ibiracatu. Only 30% of these trees were healthy, showing no visible signs of wood borer attack on their trunks (Lepidoptera: Cossidae) or of Phomopsis sp. attack on their branches (Fungi). The trees at these sites had a lower percentage of healthy branches than the percentage found for other areas (Table 1). 91% of the C. brasiliense trees surveyed in the Ibiracatu municipality, both in the Savanna and in the pasture, showed symptoms of attack by Phomopsis sp. or had branches with dry tips (data non showed). An additional finding was that this fungus attacked 85% of the C. brasiliense seedlings (data non showed). We did not detect significant effects of the height or width of the C. brasiliense canopy or of the DBH on the percentages of healthy trees, live trees or healthy branches/C. brasiliense tree (Table 2). However, LEITE et al. (2011b) has observed higher numbers of pupae and of sawdust produced by Cossidae in C. brasiliense trees having a DBH of over 30 cm.
The C. brasiliense trees having a greater canopy height and width, a greater DBH and a higher frequency of plants in the larger floristic-diversity size categories occurred in pasture 1 of Montes Claros and in Savanna and pasture in Ibiracatu. Moreover, C. brasiliense trees of smaller sizes and associated with higher frequencies of plants in the smaller floristic-diversity size categories were located in the Savanna of Montes Claros (Tables 1 and 2).
The study areas showed a low rate of natural regeneration of C. brasiliense (a low percentage of seedlings). The study found that the percentages of plants below 2.0 m and above 3.0 m in height (reproductive phase) at the Montes Claros sites were as follows: Savanna, 0.0 and 75.0%, respectively; pasture 1, 2.3 and 95.4%, respectively; pasture 2, 6.3 and 87.5%, respectively; and pasture 3, 7.6 and 78.2%, respectively. The corresponding values for Ibiracatu were 0.0 and 90.0%, respectively, in Savanna and 5.0 and 80.0%, respectively, in pasture (Table 2). A low rate of regeneration has also been observed by LEITE et al. (2006) in other areas of Montes Claros.
We observed that C. brasiliense trees in areas whose soils contained higher total levels of bases (calcium + magnesium + potassium) and total sand (fine + gross) were less healthy. Moreover, the areas whose soils contained higher levels of aluminum and clay had a higher percentage of healthy C. brasiliense trees and healthy branches (Figure 1). Higher values of the summed bases and of aluminum and silt and clay and lower values of fine and gross sand were observed in pasture 1 in Montes Claros (Table 3).
Smaller percentages of living and healthy trees and healthy branches were observed in areas with higher floristic diversity (Figure 1). The lowest density of C. brasiliense trees ha-1 was observed in the Savanna in Montes Claros (Table 1). Higher numbers of trees groves-1 of other species and shrubs were noted in the Savanna in Ibiracatu.
A higher percentage of plant cover (less bare soil) was found in pasture 1 in Montes Claros and in pasture in Ibiracatu (Table 1).
C. brasiliense is a tree typical of the Brazilian Savanna. The Savanna soils are generally deep and loamy (providing an excellent storage capacity for rainwater), poor in nutrients, rich in aluminum and generally exhibit an acidic pH (SOUSA; LOBATO, 2004). These properties favor the development and productivity of this species (LEITE et al., 2006). Of the six areas studied, pasture 1 in Montes Claros was the only area with clay soil, higher acidic pH and higher aluminum content. Likely because of these characteristics, it was also the area that had trees with the greatest canopy height and width and the greatest DBH as well as a high percentage of living and healthy trees. In contrast, the Savanna in Ibiracatu has a relatively sandy soil with a less acidic pH and lower aluminum content. These characteristics make the C. brasiliense trees more vulnerable to attack by the trunk wood borer (LEITE et al., 2011b) and by the fungus Phomopsis sp. LEITE et al. (2011b) has observed higher numbers of cossid pupae and more sawdust produced by Cossidae in C. brasiliense in soils that had higher levels of potassium, calcium, magnesium, summed bases, cationic exchange capacity and organic matter and lower amounts of fine sand.
The Brazilian Savanna has been deforested for grain and cattle production (AGUIAR; CAMARGO, 2004), besides reforestation with eucalyptus (ZANUNCIO et al., 2002). However, the C. brasiliense tree is protected by federal laws and is left in deforested areas of the Brazilian Savanna (LEITE et al., 2006). Farmers have left reserve forest areas in which the soils exhibit poor physical structure (more sandy or stony), as noted in areas of Savanna in Ibiracatu and Montes Claros.
These soils reduce the production and natural regeneration of C. brasiliense (LEITE et al., 2006). In pastures, the rate of natural regeneration (seedlings) of C. brasiliense is also low. Although the soils contain more clay, the seedlings of the tree are constantly pruned by using hooks, are burned during the cleaning of the pasture or are eaten by cattle (LEITE et al., 2006). Moreover, in both the pasture and the Savanna the fruit collectors remove virtually all of the fruits of the C. brasiliense. Thus, they reduce the natural propagation of this plant considerably. These factors can result in a serious risk of extinction for C. brasiliense (LEITE et al., 2006).
C. brasiliense is a typical Savanna tree. Savanna sensu stricto is characterized by the predominance of the herb-shrub stratum and by the presence of a few tree species (ALMEIDA et al., 1998). This pattern may explain our observation that a higher percentage of dead and diseased C. brasiliense trees was associated with increased numbers of groves and trees. The reason for this association may be increased competition for nutrients, water and light in areas where soils are sandier. Furthermore, the more humid microclimate produced by vegetation growing around the C. brasiliense trees may favor the fungus Phomopsis sp. to a greater extent than the microclimate of more open and sunny areas (i.e., pasture). In addition, other trees can be natural hosts of the fungus (e.g., Hancornia speciosa Gomez, Myracrodruon urundeuva Fr. All.) (ANJOS et al., 2001) and can serve as a source of infection for other plants.
However, areas with lower floristic diversity, particularly areas that have few trees of other species, may cause the attacks of Cossidae to be concentrated on the trunks of C. brasiliense (LEITE et al., 2011b). The damage to the trunk of C. brasiliense caused by this insect can be serious and can lead to death (LEITE et al., 2011b). Nevertheless, we do not believe that this insect is the main source of the mortality of C. brasiliense in the areas studied, especially in the Savanna in Ibiracatu. However, this area does show evidence of past insect attacks on C. brasiliense trees. The area has a relatively high incidence, among the areas studied, of hollow trunks with damage by this insect (LEITE et al., 2011b). However, we think that one of the major sources of mortality of C. brasiliense is the fungus Phomopsis sp., which is the cause of a disease that kills the tips of the branches of this plant (CARVALHO, 2007) and attacks its leaves (ANJOS et al., 2001). This source of mortality must be considered along with the presence of very sandy soil and a greater competition for nutrients, water and light with other trees. However, the biggest problem observed in this study is not simply the mortality of C. brasiliense but the fact that this mortality reflects the general idea that the Savanna is a 'patient' that has been depleted and degraded in the north of Minas Gerais State.
Caryocar brasiliense trees, in areas where the soils contained higher levels of summed chemical bases and total sand, are less healthy. Smaller percentages of live and healthy trees and healthy branches are noted in areas with higher floristic diversity. Overall, the higher mortality of C. brasiliense trees may be associated with a higher pH and a lower content of aluminum, silt and clay, with competition with other tree species for nutrients, water and light, with the attack of Cossidae and particularly with the attack of fungi, Phomopsis sp.
To the Brazilian agencies 'Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)' 'Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)', 'Prefeitura de Ibiracatu e a EMATER de Ibiracatu', the 'Coordenação da Promotoria Pública de Justiça do Rio São Francisco (Sub-Bacia do Rio Grande Verde) and the 'Instituto Grande Sertão'.
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Received on April 9, 2011.
Accepted on June 10, 2011.
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